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MAYON VOLCANO BULLETIN 23 November 2014 8:00 A.M.

Sunday, 23 November 2014 07:40

Mayon Volcano’s current condition remains unstable due to slow but sustained ground deformation of the edifice by subsurface magma since the start of unrest this year. Data from the latest ground deformation survey on November 9 - 13 indicated a deflation of the edifice relative to the October 21 – 28 survey, although the edifice remains inflated relative to the baseline measurements beginning 2010. The deflation may have been caused by short-term depressurization of intruded magma at depth or by magma having risen to shallower depths. Continuous observation will be conducted to determine if this episode of deflation persists without the emergence of other precursors, since past eruptions have occurred during the deflationary trend in ground deformation. Short-term deflation was also reflected by electronic tilt data from the continuous network on the northwest flank, although continuous inflation of the edifice has been detected since August 2014, succeeding a previous inflation event in June to July 2014. The inflation events correspond to batches of magma (approximately 107 cubic meters) that have been slowly intruded at depth but that have yet to be erupted at the crater, and therefore posing threat of eventual hazardous eruption at an unknown time in the near future.

Meanwhile, Mayon’s seismic network detected three (3) volcanic earthquakes during the past 24 hours, consistent with overall slow magma intrusion at depth that has characterized this year’s activity. Emission of white steam plumes was of moderate volume that drifted west-southwest and west-northwest. Crater glow was observed at Intensity I last night, while sulfur dioxide (SO2) emitted at the crater averaged 106 tonnes/day on 09 November 2014, which is below the baseline level during normal periods. The visual and gas parameters may denote either poor magma degassing or the generally low gas content of intruding subsurface magma. Seismicity, visual and gas parameters, however, may suddenly change within a few hours or days should magma breach the surface in an eventual eruption.

Mayon Volcano’s alert status remains at Alert Level 3. At this present stage, potentially eruptible magma has already been intruded and continues to be intruded beneath the edifice. At any given time in the following weeks to months, this magma can eventually be erupted quietly as lava flows or explosively as vertical eruption columns and pyroclastic flows or both. It is strongly recommended that the 6-km radius Permanent Danger Zone (PDZ) around the volcano and the 7-km Extended Danger Zone (EDZ) on the southeastern flank be enforced due to the danger of rock falls, landslides and sudden explosions or dome collapse that may generate hazardous volcanic flows. PHIVOLCS maintains close monitoring of Mayon Volcano and any new development will be communicated to all concerned stakeholders.